In Patent Literature No. 1, an optical waveguide element that is applicable to an optical modulator and the like is described. The optical waveguide element that is described in Patent Literature No. 1 includes plural optical waveguide parts which are arranged on a substrate in proximity to each other and in parallel with each other, and plural modulation electrodes which apply an electrical field based on an independent modulation signal (control signal) to each of the optical waveguide parts.